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LMX2594: Power control as a function of OUTx_PWR and divider state

FarronDacus
Intellectual 780 points
Part Number: LMX2594

Hello: 

In the LMX2594, it is noted that the current to the output buffer increases for OUTx_PWR states 0 to 31 and then again from states 48 to 63. States 32 to 47 are redundant and mimic states 16 to 31.  A setting of 50 is generally recommended for maximum power.

Can it be reported what the RF power is as a function of the value of OUTx_PWR?

If it cannot be accurately reported, then can the approximate range of power as a function of OUTx_Pwr be given?  By this, I mean the approximate dynamic range of power control, such as "About 20dB" or whatever it tends to be. 

Can it be reported what the current in the output stage is as a function of OUTx_PWR? 

Also, is the output power about the same regardless of whether it is the direct VCO signal or the divider output that is routed to the output amplifier?  If not, can the difference be approximately quantified?

What I am really after understanding is if the OUTx_PWR setting can be used as a reliable RF power control feature, and over about what dynamic range of power. 

Thanks,

Farron

  • 0
    TI__Guru** 108630 points

    Hi Farron,

    Datasheet Figure 20 has the plot of OUTx_PWR vs output power. 

    Output power depends on output frequency; OUTx_PWR; output pull-up and trace length. There are several plots in the datasheet giving these data. 

    In summary, we did not pay effort to make the power control in hi-fi quality. You may need to develop a power adjustment network to have a fine control to the output power.

  • 0 in reply to Noel Fung
    Intellectual 780 points

    Hi Noel:

    Thanks very much--that figure answers my question perfectly. 

    I had missed it because I did not have the latest datasheet and it was not in the previous one.  Sorry to waste your time on that. 

    ...Farron